Variable-Throat Turbocharger Scroll Design
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Solution Overview
Problem
Existing radial flow type variable-throat exhaust turbochargers face challenges in increasing the A/R ratio of the scroll passage to enhance turbine capacity without enlarging the turbine casing, which complicates manufacturing and increases costs.
Innovation Solution
A variable-throat exhaust turbocharger design featuring a nozzle assembly unit with a rotatably supported nozzle vane arrangement and an annular nozzle plate that forms part of the scroll chamber's inside sidewall, allowing for increased cross-sectional area without expanding the casing, combined with a seal member to prevent gas leakage and a ductile nozzle plate for reduced weight and improved aerodynamics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If cross sectional area A of the convolute passage is increased to enhance turbine capacity, then the A/R ratio improves, but the turbine casing size increases
Solution Approach 1:
The scroll chamber is extended in the axial direction rather than radially, changing the dimensional approach to increase cross-sectional area. This allows the convolute passage to achieve larger area while maintaining compact radial dimensions, thereby improving A/R ratio without significantly increasing overall casing volume.
Solution Approach 2:
The nozzle assembly unit with variable-throat mechanism is integrated within the scroll chamber structure, with the nozzle vanes arranged in the annular flow passage formed by the scroll chamber. This nested arrangement optimizes space utilization, allowing the convolute passage to achieve larger effective area while keeping the casing compact.
2Power
If scroll radius R is decreased to increase the A/R ratio, then turbine capacity improves, but the annular flow passage for nozzle vanes cannot be accommodated
Solution Approach 1:
The design resolves the spatial conflict by extending the scroll chamber axially rather than compressing it radially. This dimensional shift allows the convolute passage to achieve larger cross-sectional area without reducing scroll radius, thereby maintaining the necessary annular flow passage dimensions for nozzle vanes while improving A/R ratio.
3Power
If the scroll chamber is extended axially to increase cross sectional area, then the A/R ratio improves, but manufacturing complexity increases
Solution Approach 1:
The turbocharger is divided into modular components: the scroll chamber as a separate casting, the nozzle assembly unit as an independent module, and the turbine rotor. This segmentation allows each component to be manufactured and assembled separately, simplifying the core formation process for the scroll chamber while maintaining the beneficial axial extension for increased A/R ratio.
Solution Approach 2:
The nozzle assembly unit is integrated within the scroll chamber structure, with the annular flow passage formed by the scroll chamber accommodating the nozzle vanes. This nested design allows the convolute passage to achieve larger effective area while keeping the casing compact.
4Reliability
If a seal member is added between the nozzle plate and turbine casing to prevent gas leakage, then reliability improves, but device complexity increases
Solution Approach 1:
The seal function is integrated into the nozzle assembly unit by providing a seal member between the nozzle plate and turbine casing. This combination ensures reliable gas sealing at the critical interface where the scroll chamber and annular flow passage meet, preventing exhaust gas leakage while maintaining a compact overall structure.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This design enhances turbine capacity, approaches constant-pressure turbocharging, increases efficiency, and simplifies the manufacturing process by reducing the turbine casing size and weight while maintaining or improving engine performance.
Implementation Method 1
a seal member is provided between the nozzle plate and turbine casing for sealing against gas leakage between the scroll chamber and the downstream side of the annular flow passage
Implementation Method 2
engine exhaust gas is introduced to the scroll chamber to pass through the annular flow passage to flow into a radial flow type turbine
Implementation Method 3
the exhaust gas exerts forces to rotate the turbine rotor... expands therein to transmit expansion work thereto
Data Source
AI summary
A ratio of cross sectional area A of a scroll passage to a scroll radius R (A/R) can be increased without increasing the size of a turbine casing and with very simple construction. An exhaust turbine capacity can thus be increased, so that a variable-throat exhaust turbocharger in which the engine output can be increased results. The turbocharger has a nozzle throat area varying mechanism of which a nozzle assembly unit is composed. A plurality of nozzle vanes are supported rotatably by an annular nozzle mount and an annular nozzle plate is connected to the nozzle mount by a plurality of nozzle supports to sandwich the nozzle vanes. The nozzle plate is located in the scroll chamber by attaching the nozzle assembly unit to the turbine casing to allow the nozzle plate to form part of the inside sidewall face of the scroll chamber and a wall face of the annular flow passage.